ML19259D358
| ML19259D358 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/27/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R VERMONT YANKEE NUCLEAR POWER CORP. |
| References | |
| NUDOCS 7910180197 | |
| Download: ML19259D358 (1) | |
Text
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o UNITED STATES
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NUCLEAR REGULATORY COMMISSION 3'
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,o KING OF PRUSSIA, PENNSYLV ANIA 1940G Docket No. 50-271 SEP 271m Vermont Yankee Nuclear Power Corporation ATTN:
Mr. Robert H. Groce Licensing Engineer 20 Turnpike Road Westborough, Massachusetts 01581 Gentlemen:
The enclosed 3ulletin 79-24 is forwarded to you for action. Written responses are required.
If you desire additional information regarding this matter, please contact this office.
Sincerely,
. D
/ h YAl oyce H. Grier Director
Enclosures:
1.
List of IE Bulletins Issued in the Last Six Months cc w/encls:
W. F. Conway, plant Superintendent Ms. J. Abbey, Technical Secretary A. Z. Roisman, Natural Resources Defense Council 116/
165 G 7910180 M
ENCLOSURE 1 Accession No. 7908220114 SSINS No:
6820 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 79-24 Date:
September 27, 1979 Page 1 of 2 FRUZEN LINES Summary:
On January 3, 1979, an unusual event occurred at Davis-Besse, Unit 1.
The event involved the freezing of the water in a portica of the high pressure coolant injection (HPCI) system recircC ation line that is common to both high pressure coolant injection pumps.
The line was not thawed until January 5, 1979, and the event was not reported to NRC ur,til March 12, 1979.
In addition, over the past five years, there have been several ever.ts involving frozen instrument and sampling lines.
Description of Circumstances:
The condition was discovered on January 3, 1979, while the reactor was operating at approximately 96 percent power.
During a monthly surveillance test of the HPCI pumps, there was no flow through the recirculation line from the pump discharge to the Borated Water Storage Tank (BWST).
Investigation revealed that water in a portion of the line exposed to the outside weather was frozen.
This portion of the line to the BWST is common to both HPCI pumps.
The line has redundant heat tracing (a heated wire to prevent freezing); it is insulated; and it has a low-temperature alarm system to warn of freezing conditions.
Water in the line froze apparently because of prolonged sub-freezing temperatures and a defect in the insulation.
There was no apparent malfunction of the heat tracing or temperature alarm circuits, although the temperature sensing elements are located in an area not exposed to the coldest temperature conditions.
This recirculation line serves two purposes:
One is to provide a flow path for surveillance testing, and the other is to provide a minimum flow path to prevent possible damage to the pump in the event it is operated against a closed discharge valve or a reactor coolant system pressure greater than the maximum discharge pressure of the pump (approximately 1600 psig).
In the initial review of the event on January 3. 1979. the licensen enneludad that the pumps were still operable wit no immadiate action was taken to thaw Janur-5, 1979, the line was thawed a was e assfully completed.
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